1. Field of the Invention
The present invention relates, in general, to a reclosing control system and method using a superconducting fault current limiter, and, more particularly, to a reclosing control system and method using a superconducting fault current limiter, which determine a reclosing time in consideration of the recovery time of a superconducting fault current limiter, thus adjusting the fixed dead time of a conventional scheme.
2. Description of the Related Art
A recloser, which is one of a plurality of protection devices used in a power distribution system, is used to restore the system when a transient fault occurs. In a power distribution system, most faults are transient faults, and thus power quality and reliability can be improved by reclosing.
A conventional recloser has a fixed dead time (for example, 0.5 sec or 15 sec). Such a conventional recloser is designated to perform reclosing after a preset reclosing time has elapsed even if a fault is promptly cleared. Further, a conventional recloser cannot determine whether a current fault is a permanent fault or a transient fault for a dead time even if the fault is cleared, and can merely determine whether the current fault is a permanent fault or a transient fault by using current flowing when the system is closed after the dead time.
In this case, conventional technology for determining whether a transient fault has occurred may include a method of determining the extinction time of secondary arc using the effective value (or root mean square: rms) of a fault voltage and a method of determining the extinction time of secondary arc using the Total Harmonic Distortion (THD) of a fault voltage. These methods are mainly investigated in a power transmission system in which the capacitance of a line is large. In a power distribution system, research into techniques for determining a permanent or transient fault has scarcely been conducted.
Meanwhile, with the large-scale and complexity of a power system, fault current also greatly increases, so that the case where protection devices cannot resist the high fault current and consequently fail to interrupt the high fault current may occur. As a solution for such a case, research into the application of a Superconducting Fault Current Limiter (SFCL) to the power system has recently been widely conducted.
In order to connect the SFCL to the system, protective cooperation with other protection devices must be considered. In the aspect of protective cooperation with a recloser, which needs to be considered, there exist a variety of problems, such as malfunctioning due to the setting of pick-up current and the conflict between recovery time of the SFCL and the reclosing time of the recloser. In a case such as this, the problem of the setting of pick-up current can be easily solved by means of a setting performed when products are manufactured. However, there is a problem because it is difficult to solve the problem of the conflict between the recovery time of the SFCL and the reclosing time of the recloser.